This .csv file has a few places in North Texas, South Oklahoma and Western Arkansas where you can legally ride dirtbikes and ATV's. Most are on private property and the owners charge a fee ($10-$15) to ride there. The acreage ranges from about 500 acres to just over 2000. The Lake Murray area is run by Oklahoma State Parks, who charge a $7 fee.
I have been to all of these parks. I plan on updating this list with places I have not been, as times allows. East Texas has plenty more riding specific to ATVer's who like the mud. Arkansas also has some beautiful trails in the Ouchita National Forest area around Mena Ark.